Electric alarm system



July 26, 1955 MURPHY 2,714,203

ELECTRIC ALARM SYSTEM Fi'led June 28, 1951 NSULATION Ida/1Z3 Z. M/

United States Patent ELECTRIC ALARM SYSTEM Edwin L. Murphy, Mouee, Ill.

Application June 28, 1951, Serial No. 233,963

8 Claims. (Cl. 340-216) This invention relates to improvements in electrically operated alarms and refers particularly to an alarm of simplified construction which may be conveniently connected into the usual service current of a building, house or other area.

One of the important features of my invention resides in an alarm circuit, component elements of which, that is, detection element and alarm element, may be plugged into any conventional outlet of the usual house or build ing wiring system.

Another important feature of the invention resides in the flexibility of the invention wherein the detection element and the alarm element may be connected in the same branch circuit of the wiring system, or the detection element may be connected into one branch circuit and the alarm element may be connected into another branch circuit, or as many detection elements as desired may be employed on anybranch circuit or circuits, and as many alarm elements may be connected in each or any branch circuits as desired.

A further important feature of the invention resides in the provision of means whereby external current failures will not render the system inoperative after the supply or current is resumed.

Other objects and advantages of the present invention will be apparent from the accompanying drawing and following detailed description.

In the drawing,

Fig. 1 is a schematic drawing, parts being shown diagrammatically of my improved alarm system.

Fig. 2 is a partially diagrammatic, partially schematic drawing of a modification of a portion of the system illustrated in Fig. 1.

Referring in detail to the drawing, 1 indicates a detection element together with circuit and parts thereof enclosed in broken lines intended to indicate its unitary character; 2 indicates an alarm element similarly designated as being unitary and 3 indicates the fuse distribution center of the usual service wiring together with additional circuit elements and parts for adapting the wiring system to my invention. Fuse distribution center, as contemplated herein is intended to mean the box or cabinet where the branch circuits are taken off the mains. Of course, although fuses as protective circuit opening devices are shown and described herein, it is to be understood that circuit breakers of the thermal or magnetic type are also contemplated.

The conductors 4 and 5 indicate the main line to which branch circuits 6 and 7 are connected. My invention is adaptable for use with building or house wiring systems where one or more fused branched circuits are employed. However, for purposes of illustration a house wiring system containing two fused branch circuits 6 and 7 are shown, the main fuses for each of the branches being shown at 8 and 9, respectively.

Associated with each branch circuit 6 and 7 is an arm, 10 and 10, respectively, pivoted at 11 and 11. Each arm 10 and 10 is spring biased by means of springs 12 ice and 12', respectively, tending to swing said arms in a counterclockwise direction about their respective pivots, as viewed in Fig. 1. Fuse elements 13 and 13' are respectively associated with arms 10 and 10, said fuse elements carrying hooks 14 and 14 which support said arms and prevent rotation of the arms. The fuse elements have a maximum current-carrying capacity of about .25 ampere and are sufficiently strong structurally to support the respective spring-urged arms.

Arms 10 and 10' are constructed of an electrical conducting material and are respectively connected to one side of the main branch fuses 8 and 9 respectively by conductors 15 and 15. The opposite sides of the fuses are connected by conductors 16 and 16' to the fuse elements 13 and 13, respectively. The ends of arms 10 and 10' respectively terminate in shoes 17 and 17' which are constructed of insulating material, such as, hard rubber, plastic or hard fibre. Normally open switches 18 and 18' are associated with each of the arms 10 and 19, respectively, one side of switch 18' being connected by means of conductor 19 to line 5 and the other side being connected by means of conductor 20 through main branch fuse 8 to the opposite line 4. Switch arms 10 and 10' carry contact points 21 and 21, respectively, said points comprising companion points to the points 22 and 22' which latter are respectively connected through auxiliary fuses 23 and 23' to the sides of the main branch fuses 8 and 9 which are common to conductors 16 and 16', respectively.

As has been hereinbefore described, the circuits included in 3 are preferably located at the branch distribution fuse center and contemplates an arrangement wherein the detection element is on one branch circuit and the alarm element is on another branch circuit.

The detection element carries terminals 24 and 25 which may be respectively connected, by the usual receptacle-plug connection (not shown) to conductors 5 and 4a, the latter being a continuation of conductor 4 through the main branch fuse 9. Terminal 24 is connected to an arm 26, constructed of an electrically conductive material, said arm being pivoted, as at 27, and being spring biased, by spring 28, to urge arm 26 in a counterclockwise direction, as viewed in Fig. 1, about the pivot point 27.

A fuse element 29, having a hook-like end 30 functions to support the spring-urged arm 26, and prevent rotation thereof. The fuse element 29 has a predetermined maximum current-carrying capacity and has suflicient structural strength to hold the spring-urged arm 26. One end of the fuse element 29 is connected by means of conductor 31, to a detection device 32.

The detection device 32 may comprise any of the conventional detection devices for protection against fire, theft, flood or the like, that is, the device may be thermally actuated, contact actuated, light actuated, resist ance actuated and in general the device comprises a switch, having contact points 33 and 34, the former being connected to conductor 31 and the latter being connected, by conductor 35 to a contact plate 36, the latter also being connected, by conductor 37 to terminal 25. The current capacity of the fuse element, 29, is lower than the current drawn by the protector device whereby the protected device current is sufiicient to blow the fuse element 29.

The alarm element 2 comprises terminals 38 and 39 the former being connected to line 5 and the latter, through conductor 4b and main branch fuse 8, to line 4. The connection between terminals 38 and 39 and the lines may, if desired, be of the conventional receptacle-plug variety (not shown) whereby the element 2 may be plugged in at anyoutlet of the branch circuit fused by main branch fuse 8.

The terminal 38 is connected by means of conductor alarmdevice43 is connectedby means of conductor 46 to;.a companionswitch point 47. An armature 48 is associated;with--the,.solenoid ;41aand: functions to actuateswitch blade 49 which isconnectedto terminal 39. It will-,be; noted that the. -cir;cuit .-comprising terminal 39, armatureAS, Switchblade-49, contact point 45 functions as; a;,ho lding cir cuit for-the solenoid 41' in: conjunction with conductor ifl which; connects tie opposite end of the, solenoidjoterminal 38 In the operation-of the device, thearmature 48 may bemanually set to make contact between-switch blade 49: and contactpoint 45 whereby the-solenoidis connectedacross the line and u functions-to-maintain its set, contact. The normal position of the switch blade 49; however, is such that it will be, in;.;contact with switch point47; the arrangement being ;such thatwhenso'lenoid 41 is deenergized, blade 49 rnakescontactwith switch point 47 and the alarm device-43 E setinto operation being connected across the'line.

In the, openation-of the device, with the armature 48 ,-.toener gize;solenoid 41, the detection device 32 U e actuated in;a manner contemplated by its intended; operation. Actuation of'the detection device 32 causes the contact points 33 and 34 to come together. It;can readily 'be seenthat a complete circuit is thus estahlislredfrom line 5' through arm 26, fuse element 29; and through conductors 37 and 4a, through main branch fuse. 93 to, line .4. Under normal 'conditionsthe current drawn by the detection device 32 is not sulficiently high to blow fuse 9. However, the current drawn by the detection device is sufficient to rupture the fuse element 29 which has a maximum current capacity considerably lower than that of the main branch fuse 9. When the fuse element 29 has been ruptured, arm 26, under the influence of spring 28, is rotated in a counterclockwise direction, as viewed in Fig. 1. During the rotation of thearm 26, the end thereof, which is also of conducting material, wipes upon and makes electrical contact with the contact plate 36. The end of arm 26 is relatively resilient-and is adapted to move past the contactplate 36 and eventually comes to rest at stop pin; 50.- However, as arm-26; makes contact with the plate 36 a dead short is placed across the lines 4 and Sand sufiicient instantaneous current flows to cause fuse 9 to bedisrupted.

With the blowing of fuse- 9 the fuse element 13 being in-parallel therewith and being of a current capacity less thanfuse 9, also blows and arm 10 is rotated in a. counterclockwise direction, as viewed in Fig. 1, under the-influence of spring 12f. As arm 10' rotates it eventually comes torest with contact'points 21'- and 22 makingelectrical contact and hence the line circuit between line conductors 4aand 5 ismaintained through the auxiliaryfuse'33'. which has a current carrying capacity equal to that of the fuse 9. Consequently, the normal function of the branch circuit comprising the lines 411 and 5 is maintained and electric lights and other appliances which may be connected to said branch circuit will be maintained in operation except for the short period of time during the movement of arm 10' from its normal position to its position-wherein contacts 21'- and 22 come together.

During the travel of arm 10 from its normal supported position to the'position wherein the auxiliary fuse 23' is placed; in circuit, the: insulating shoe 17 makes wiping contact with one side of the switch .18 whereby the cir-. cuit is ,completedbetweeu conductor; 20. and. line 5; 1t

will be noted that this places the main branch fuse 8 directly across the line and said fuse blows. When the fuse 8 blows the circuit to solenoid 41 is momentarily opened and hence armature 48 leaves solenoid 41 and switch point 49 makes contact with the switch point 47. In this fashion the alarm device 43 is placed directly across the line.

At the time that the main branch fuse 8 blows, the fuse element 13 is placed in circuit and it also is disrupted and arm 10, under the influence of spring 12, swings in a counterclockwise direction, as viewed in Fig. 1, until contacts 21 and 22 are together at which time the auxiliary fuse 23, having a maximum current capacity equal to fuse 8, is placed in circuit. By this means the branch circuit which was normally fused by the fuse 8 is now fused by the auxiliary fuse 23 and all current consuming devices connected between lines 43 and 5 are maintained in operation includingthe alarm device 43.

When an alarm has been set off as described hereinbefore and it is desired to restore the circuits to their normal operating conditions, fuses 8 and 9 are replaced and fuse elements 29, 13 and 13' are replaced-and associated with the respective arms which they support in the position shown in Fig. 1. The armature 48 is also manually reset to bring switch blade 48 into contact with contact point 45 to again place solenoid 41 in circuit.

In the event that the detection. element 1 and alarm element'2 are connected on the same branch circuit, the lines 4a and 411 will be the same lines and, hence, upon the blowing of the single main branch fuse 8 or 9, depending upon which branch circuit the elements are connected, the solenoid 41 -will be deenergized and the alarm device will be actuated. I

Referring particularly to Fig. 2, circuits and diagrammatically shown apparatus are illustrated which may be substituted for parts hereinbefore described in Fig. 1. It will-be noted in the arrangement shown in Fig. 1 that the presetting of the alarm section is dependen upon continuity of current in lines 4.,and 5. If, as sometimes happens, a temporary power failure occurs, so-.

lenoid 41;will be, deenergized and switch blade 49 will contact the contact point 47 which places the alarm device 43 in circuit where it will be actuated when power is resumed. By employing the elements constituting Fig. 2 in place.- of certainof the elements in Fig. 1, a power failure will not operate to, set off the alarm.

In Fig. 2, element 51,may be substituted for alarm element Z and element 52 maybe substituted for the elements and circuit shown at the right hand portion of element 3 of Fig. 1. i

In Fig. 2 solenoid 53 is connected across the lines.4 and 5 through the'main branch fuse 54 and line 412. The. element 51 may be constructed as a unit and may be plugged into the branch circuit, in themanner contemplated for the element 2. A core 55 is associated with solenoid 53 and when the latter is energized, the core occupiesthe position shown in Fig.- 2. A- coil spring 56 is connected to the core 56 and tends tourge core 55 upwardly against the pull of the energized solenoid. A lever- 57, pivoted at one end, as at 58, is connected to an intermediate portion thereof to, solenoid 55, whereby. movement of the lever in a.clockwise direction, as viewed in Fig. 2, aboutthe pivot 58 swings the outer endof the lever upwardly.

A pawl 59 is pivotally connected intermediate its length to the end .of lever 57-. and the upper-end of said pawl is connected by tension coil spring 60. to an intermediate portion of lever57, whereby said spring tends to rock the pawl59 in .a clockwise direction, as viewed inFig. 2, about itspivoted connection to lever 57. A fixed pin is disposed adjacentabent portion 62 of pawl 59, said pin controlling. the clockwise motion of the pawl when the lever 57 and pawl 59 are raised.

A ratchet wheel 63, circular dial64 and circular dial 65 are diagrammatically shown as being carried by shaft 66. Shaft 66 is under the influence of helical spring 67 which normally urges said shaft so as to move the ratchet wheel and the two dials in a counterclockwise direction, as viewed in Fig. 2. In the normal position of pawl 59, that is, when coil 53 is energized, shoulder 68, formed on said pawl has been moved clear of the adjacent tooth of the ratchet wheel 63 by the engagement of the bent position 62 of the pawl with the pin 61. Accordingly, under normal conditions the shoulder 68 does not restrain the counterclockwise movement of ratchet wheel 63.

A second pawl 69 is disposed adjacent the ratchet wheel 63 and normally engages with an adjacent ratchet tooth to prevent counterclockwise movement of the ratchet wheel. Pawl 59 comprises a part of a bimetal strip 78 which, when heated, buckles upwardly and causes pawl 69 to disengage itself from the ratchet tooth.

Dial 64 carries a rim portion 71 which is constructed of an electrical insulating material and a segment 72 of said ring is constructed of an electrical conducting material. Dial 65 carries a rim portion 73 which is constructed of an electrical insulator and a segment 74 of electrical conducting material. A pair of spaced brushes 75 ride upon the rim of dial 64 and a pair of spaced brushes 76 ride upon the rim of dial 65. An alarm device 77 is connected through the two brushes across lines 4b and 5. An electric heating element 78 is connected at one end, by means of conductor 79, to one of the brushes 76 and at its opposite end, by means of conductor 80 to line 5. The heating element 78 being disposed adjacent to the bimetal strip 70 which controls pawl 69.

For purposes of reference, the teeth upon the ratchet wheel 63 are numbered from 1 to 8 and the rim of dials 64 and 65 are likewise divided into segments numbered l to 8. It will be noted that segments 1 to 7 on dial 64 inclusive are insulating segments and that segment 8 is a conducting segment, and that segments 2 to 7 inclusive on dial 65 are conducting segments and segments 1 and 8 are insulating segments. The normal initial setting of the ratchet wheel and dials 64 and 65 is as shown in Fig. 2. In this position the alarm device is rendered inoperative since brushes 75 are not interconnected.

If a power failure occurs, solenoid 53 is deenergized and core 55 raises under the influence of spring 56. Lever 57 is thereby swung in a clockwise direction about pivot 58 and pawl 59 is raised. As pawl 59 raises, said pawl simultaneously swings clockwise under the influence of spring 66, the swinging movement being controlled by the contact of the shoulder portion of the pawl and the side of the tooth 1, end 62 and pin 61. When shoulder 68 has moved upwardly along the side of tooth 1 a sufficient distance for the shoulder to clear the top of tooth 1 said shoulder moves over the top of tooth 1 into operative engagement with said tooth. Of course, the

.power being oif, the parts remain in this position until the power is resumed.

Upon the resumption of power, core 55 is moved downwardly, thereby moving lever 57 and pawl 59 downwardly; The downward movement of pawl moves ratchet wheel 63 and shaft 66 clockwise but alarm 77 will not have been actuated since the brushes 75 remain disconnected. Pawl 59 will have been moved to the position shown in Fig. 2, and by virtue of the contact of pin 61 with the pawl end 62 the pawl will move clear of the tooth with which shoulder 68 was previously engaged and the pawl 69 now holds ratchet wheel against movement. However, when shaft 66 has been moved, as previously described, rim 74 will connect brushes 76 together, completing the circuit of heater 78. After an interval of time the heat from the heater 78 will cause the bimetal strip 70 to buckle, thereby causing disengagement of pawl 69 and its adjacent tooth. Shaft 66 and its 6 accompanying members will then return under the influence of spring 67 to the normal position illustrated. Accordingly, a power failure followed by a resumption of power wherein the period of resumption of power is of sufiicient duration to heat the bimetal strip 70 always results in a return of the parts to their normal position.

The element 52 is preferably located at the distribution fuse center and supplants the parts and the circuit illustrated in the right-hand portion of element 3 in Fig. 1. The element 52 comprises a shaft 81 which is biased by a helical spring 82 normally tending to rotate said shaft in a clockwise direction as viewed in Fig. 2. A Wheel 83 and a wheel 84 are rigidly carried upon shaft 81. A normally open switch 85 is positioned adjacent the wheel 83, said switch comprising a contact point 86 which is connected by means of conductor 87 through auxiliary fuse 88 to line 4. The switch also comprises a spring contact blade 89 which is connected by means of conductor 98 to conductor 19a which corresponds to conductor 19 in Fig. 1. The wheel 83 carries a plurality of spaced protuberances upon its periphery, said protuberances being numbered from 2 to 8 inclusive.

An arm 91 is carried upon the periphery of wheel 84, saidarm, normally, being restrained by a fuse element 92 which is looped about the arm 91 and prevents rotation of the wheel 84 and hence shaft 81 under the influence of spring 82. The fuse element 92 is connected between conductor 19a and 20a, the latter being a continuation of the conductor 20 shown in Fig. 1.

As has been hereinbefore described, the circuits and parts illustrated in Fig. 2 are adapted to be employed with element 1 shown in Fig. 1 and the left-hand portion of element 3 shown in Fig. l. The conductors 19a and 20a in Fig. 2 comprise continuations of the conductors 1.9 and 2t) shown in Fig. 1, said conductors being connected to the switch 18. As has been hereinbefore de scribed, when the detecting device 32 is actuated to bring contact points 33 and 34 to electrical contact the various members of element 1 and the various elements of the left-hand portion of element 3 shown in Fig. 1 are so actuated as to close switch 18' when the insulating shoe 17 carried by arm 10 moves past the switch 18. When the switch 18' is momentarily closed fuse 54 (Fig. 2) is blown as is the fuse element 92. In the normal position of the wheel 83 the spring switch blade 89 is spaced from the first protuberance 2 so as to cause switch 82 to normally be open. However, when the fuse element 92 is ruptured the spring 82 causes rotation of shaft 81 in a clockwise direction, as viewed in Fig. 2. Hence, the first protuberance 2 contacts the spring blade 89 and closes switch 85.

In the meantime after fuse 54 has blown coil 53 was deenergized and consequently pawl 59 was moved upwardly to a position whereby it can engage tooth 1 of the ratchet wheel 63. When switch 85 is closed by contact with the protuberance 2 the circuit to coil 53 is again closed and the core moves downwardly thereby rotating ratchet wheel 63 and shaft 66. It will be noted, however, that the protuberance 2 momentarily closes switch 85 and consequently the current which would normally pass through the heating element 78 since the dial has been moved so as to place the brushes 76 upon the conducting rim 74, is not maintained for a sufiiciently long period of time to heat the bimetal strip sufficiently to cause it to buckle. Accordingly, the ratchet wheel 63 will be maintained in its first advanced position by the pawl 69.

As the wheel 83 continues to rotate protuberances 3 to. 8 inclusive function to momentarily close switch 85 and at each close of said switch the solenoid 53 is energized between periods of deenergization. In this fashion the ratchet wheel 63 is progressively rotated in steps until the segment 72 upon the dial 64 bridges the brushes at which time the alarm device 77 is actuated. It will be noted that at this period brushes 76 rest upon segment 8 of dial 65 which comprises an insulating portion 73 of the rim'of the dial and hence the heating element'78 is not rendered active.

It can readily be seen, therefore, that by employing the parts and circuit comprising Fig. 2 in place of the corresponding parts and circuits shown in Fig. 1 the arrangement can withstand periodic power failures without destroying the preset condition of the system and without prematurely or accidentally actuating the alarm device. However, when the detecting device 32 is actuated the parts so function as to cause a progressive stepwise rotation of shaft -66-until the brushes 75 rest upon the con ducting rim portion 72 of the dial 64 at which time the alarm device 7 7 is placed in circuit.

Of course, after analarm has been set off and. it is desired to reset the circuit the fuse 54 and the fuse element 92 must be replaced in addition to the replacement of the other fuses which have been blown. The various parts of the apparatus may then be brought to the position shown in Fig. 2' whereat the device is again conditioned to be actuated by actuation of the detecting unit.

To prevent overrunning of the shaft 81 a stop 93 is employed against which the arm 9llabuts when the shaft 81 has consummated its intended travel. Similarly stops may be employed to limit the clockwise movement of shaft 66 at position 1 and to limit the counterclockwise rotation of said shaft at position 8 as shown on dials 64 and 65. Said latter stops are not shown.

It is apparent from the above description that an alarm system is provided which takes advantage of the existing line circuitof a house or building. The elements comprising the detection member and the alarm member may be plugged into conventional receptacles at any place throughout the building. The detection and alarm-elements may be placed upon the same branch circuit or the detection element may be placed uponone branch circuit and the alarm element placed upon the other branch circuit. In all cases the alarm will function. Employing the modification, an alarm system is suitable for districts where power failures occur more or less frequently, such power failures having substantially no effect upon rendering the alarm system inoperative. It

can alsobe seen that the elements which are consumed when the alarm is set off are relatively inexpensive elements which can be very readily and economically re-.

for reenergizing said circuit after it has been, deenergized a predetermined number of times to actuate said alarm device.

2. An electric alarm system for usev with an electric wiringcircuit connected to a permanently energized power supply comprising an alarm element and a detection element both connectedto said wiring circuit, means for transmitting a signal originating in said detection element to said wiring circuit, a circuit interrupting device in said wiring circuit to interrupt said circuit after receipt of said signal, said alarm element comprising an alarm device, means fo'rconnccting said device in said circuit after said circuit isinterrupted, and means in said wiring circuit for restoring said circuit after said interruption toactuate said alarm device.

3. An electric alarmv system for use with a fused electric wiring circuit connected to apermanentlyenergized; power supply fora building comprising an alarm elementand a detection element both connected to said wiring circuit, means for transmitting a signal origmating 1n said'detection element to said wiring circuit to disrupt 'wiring circuit for temporarily deenergizing said circuit upon receipt of said signal, said alarm element comprising an electric alarm device, electric means in said alarm element for holding said alarm device out of circuit when the circuit is energized, means for connectingsaid alarm device in circuit when said circuit is temporarily deenergized, and means in said wiring circuit to reenergize said circuit after it has been temporarily deenergized to actuate said alarm device.

5. An electric alarm system for use with a fused electric Wiringcircuit connected to a permanently energized power supply for a building comprising an alarm element and a detection. element both connected to said wiring circuit as units, means for transmitting a signal originate ingin said detection element to said wiring circuit to disrupt said fuse and render said circuit temporarily deenergized, said alarm element comprising an alarm device and means for connecting said device in said circuit when said circuitis temporarily deenergized, an auxiliary. fuse for said circuit, and means in said wiring circuit for completing said circuit through'said auxiliary fuse to reenergize said circuit after its temporary deenergization to actuate, said alarm device.

6. An electric alarm system for use with an electric wiring circuit connected to a permanently energized power supply for a building comprising an alarm element and a detection element both connected to said wiringcircuit, means for transmitting a signal originating in said detection element to said wiring circuit, means connected in said wiring circuit and responsive to said signal for alternately energizing and deenergizing said circuit a predetermined number of times to create relatively short electric impulses in said circuit, said alarm element comprising a normally open rotary switch, said alarm element also comprising means for converting said impulses to rotary movement of said switch, an electric alarm device connected to said switch, said switch being closedafter completion of said predetermined, number of electric impulses to connect said alarm device into said circuit to actuate the alarm device.

7. An electric alarm system for use. with a wiring, circuit connected to a permanentlyenergized power supply for a building comprising, a detection element and an alarm element both connected in said circuit, said detection element comprising means for transmitting an electric signal to said circuit, means in said'circuit for rendering said circuit-alternately inoperative and operative for a predetermined numberofcycles after receipt of said signal, said alarm element comprising an electrically actuated alarm device, saidalarm element also comprising means for actuatingsaid alarm device at the end of said plurality of cycles.

8. An. electric alarm system for use with a wiringcircuit connected to a permanently energized power supplyfor abuilding comprising a detection element and an alarm element both connected in said circuit, said detection element comprising means for transmitting an electric. signal to said circuit, means in said circuit for rendering said circuit periodically inoperative and operative for a plurality of pulses after receipt ofsaid signal, said alarm element comprising an electrically actuated alarm References Cited in the file of this patent UNITED STATES PATENTS 2,021,423 McBrien et al. Nov. 19, 1935 10 10 McBrien Mar. 19, 1946 Gagnaire Dec. 11, 1951 FOREIGN PATENTS Italy Jan. 8, 1938 

